A conjunction is a part of speech that connects words, phrases, or sentences. The easiest conjunctions to remember are "and" and "or." But there are conjunctions that do more than just connect—they give meaning to a sentence by expressing the time that something is happening: conjunctions of time.

You can easily tell if a conjunction of time is being used in a sentence because the sentence will tell you when something happens or for how long something is occurring. If you can make a "when" or "for how long" question from the sentence, and that question can be answered by the other half of the sentence, then you know that the sentence is using a conjunction of time.

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When

When I flew in on the float plane, they were all there on the boat.

Caption 4, Alaska Revealed - Endless Wave

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Q: When were they all there on the boat? A: When I flew in on the float plane.

Before

Be sure to put your mask on before helping them.

Caption 18, Air New Zealand - An Unexpected Briefing

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Q: When should I be sure to put my mask on? A: Before I help them.

After

They have to defend their breed from predators

for up to four weeks after they're born.

Captions 49-50, Evolution - Deep Ocean

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Q: When do they have to defend their breed? A: After they are born.

While

We have to tread lightly while filming.

Caption 40, Nature & Wildlife - Search for the Ghost Bear

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Q: When do we have to tread lightly? A: While filming.

As

We paddle along and we pick up trash as we go

Caption 23, Alison's Adventures - Your Passport To the World (LONDON)

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Q: When do we pick up trash? A: As we go.

By the time

By the time I got to New York,

I was living like a king

Captions 10-11, David Bowie - Lazarus

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Q: When were you living like a king? A: By the time I got to New York.

Note that some conjunctions of time are also phrases, not just a single word.

Until, till

The conjunctions of time "until" and "till" are interchangeable and you may use either word. Many people wrongly think that "till" is just shortened version of "until," but in fact "till" is the older word, in use since the 9th century. The variant "until" has been in use since the 12th century. These two words are unusual in that they express a length of time rather than a point in time, so we should ask the question using "for how long" instead of "when."

She sat until she broke the chair.

Caption 28, Story Hour - Goldilocks and the 3 Bears

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Q: For how long was she sitting? A: Until she broke the chair.

So he sat on a chair,

till he died of despair,

Captions 20-21, Sigrid explains - The Limerick

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Q: For how long was he sitting? A: Till he died of despair.

Further Learning
Don't despair, and by all means stay healthy! Go to Yabla English and find other sentences (not questions) that contain the conjunctions of time "when," "before," "after," "while," "as," "by the time," "until" and "till." Write these sentences down and practice making questions and answers from the sentences like we did above. You can also read more about "until" and "till" on the Merriam-Webster website.

Since we already discussed the difference between their, there, and they're in a previous lesson, perhaps it is good to also cover another common point of confusion: the words it's and its. Even native speakers get these words mixed up, so master them and you will be ahead of the game. 

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We are used to recognizing possessives by the use of an apostrophe, for example, my mother's car or the teacher's classroom. However, the word it's is not possessive, but rather a contraction of it and is used for convenience. In the sentences below, we see shortened versions of it is amazing, it is really exciting, and it is the most important part. 

And it's amazing, and they have one of the best sunsets in the world.

Caption 25, Visit Isle of Wight - Mark King of Level 42

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It's really exciting to know that I'm setting a good example for young people

Caption 26, peta2 Interviews - Vegan Surfer Tia Blanco

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That's how we know it's the most important part.

Caption 34, Rachel's English - How to Introduce Yourself - American English Pronunciation

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The word its helps us to describe how something belongs to, for example, an animal, place, or object. The sentences below are about the bear's fur, the garden's street performers, and the vest's container. 

Its fur is almost silver with a blue sheen,

the perfect adaptation to its environment.

Captions 19-20, Nature & Wildlife - Search for the Ghost Bear

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Covent Garden is famous for its street performers.

Caption 3, Christmas in London - Places

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To use, pull the tab to remove the vest from its container

and then open the pouch.

Captions 69-70, Delta Airlines - In-Flight Safety Video

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So, as you can see, “it’s” with an apostrophe is the contraction for “it is” and is never a possessive, while “its” with no apostrophe can only be a possessive and is never the contraction for “it is”.

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Further Learning
Take special note of examples of it's and its that you see while watching videos on Yabla English. Almost every video has one or both!